The present invention relates to portable tanks for storage and transport of liquids and, more particularly, to a discharge valve for a bottom discharge in such a portable tank.
Portable tanks for storage and transport of liquids typically have a bottom discharge valve for complete drainage of tank contents. The valve and associated connections are typically located near one edge so as to be readily accessible to the operator.
Butterfly or ball type valves are used on these tanks because of their generally compact and full throated design. The handle associated with these types of valves is generally rotated through an arc of approximately 90 degrees to move between the open and closed position. An elongated operating handle is typically positioned horizontally when the valve is closed and vertically when the valve is open.
Consequently, with the valve positioned at the edge and below the tank bottom, the valve handle lies in a horizontal position providing a convenient foot rest for a person standing adjacent the tank to rest his foot on. If a significant downward force is applied to the handle, the valve may be opened inadvertently discharging the contents of the tank onto the person's foot. Accordingly, it is desirable to provide a locking feature on valves of this type used in this particular application.
It is, therefore, an object of the present invention to provide a simple locking device for a tank discharge valve to prevent inadvertent movement of the valve handle from a predetermined position.
It is a further object of the present invention to provide a valve handle lock that is simple to operate and visually indicates the locked and unlocked position.
It is a still further object of the present invention to provide a readily recognizable visual message as to the position status of a tank discharge valve.
The discharge valve according to the present invention is particularly adapted for use in a metal, plastic or composite portable tank having a top wall, a bottom wall, upright sides, and a plurality of supporting legs which support the tank a given distance above the floor or other supporting surface. The discharge valve according to the present invention is positioned adjacent one of the sides and in the space between the floor and the bottom wall of the tank. The discharge valve may be of various internal construction such as a ball or butterfly type valve.
Although the following discussion describes a butterfly type valve as an example, the invention is not limited to this particular type of valve. The valve according to the present invention has a hollow body with a closable passage and has a mounting flange connected to the bottom wall at the discharge opening. A valve disk is movably supported in the passage within the hollow body. This valve disk is movable between an open position allowing passage of tank contents through the body and a closed position closing off the passage.
An operating handle is connected to the valve disk through an aperture in the hollow body via an operating shaft which moves the valve disk between the open and closed positions. A flat locking plate is bolted to the exterior of the valve body in a plane perpendicular to the axis of the shaft connecting the handle to the valve disk. A locking lever pivotally mounted on a pivot pin on the handle is movable to and from an interference relationship with the locking plate to lock the handle, shaft and valve disk in a predetermined position. This predetermined position is set by the structure of the locking plate.
The locking plate has an concave arcuate edge portion of a first radius which is centered a spaced distance from the locking plate in the plane of the locking plate. The center sets the predetermined position and is a predetermined radial distance from the axis. The locking plate also has, adjacent the concave arcuate edge portion, a convex arcuate edge portion of a second radius which is centered about the axis of the operating shaft.
The pivot pin is located on the handle the same predetermined distance from the axis as the center of the concave arcuate edge portion of the locking plate. The locking lever pivotally mounted on the pivot pin on the handle has a convex arcuate portion of the same first radius centered about the pivot pin. The locking lever also has a concave arcuate portion of a radius slightly greater than the second radius centered in the plane of the locking plate, spaced from the locking lever. The slight differences in radii provide clearance for relative movement between the locking lever and the locking plate.
When the handle is rotated to a position where the pivot pin is aligned with the center of the concave arcuate edge portion of the locking plate, the handle is in the predetermined position and the locking lever can be rotated into an interference relationship with the locking plate to prevent movement of the handle from the predetermined position.
The discharge valve according to the present invention having the concave arcuate edge portion of the locking plate having the first radius located so that the locking lever is engageable when the handle is in the closed position prevents inadvertent opening of the valve. Thus, the problem of a person putting his foot on the valve handle inadvertently opening the valve can be avoided.
Other objects, features and advantages of the present invention will become evident from a consideration of the following description when taken in conjunction with the accompanying drawing and the appended claims.